diff options
| author | Wupeng Ma <mawupeng1@huawei.com> | 2025-05-10 11:30:40 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-05-21 14:52:38 +0200 |
| commit | 1bd6406fb5f36c2bb1e96e27d4c3e9f4d09edde4 (patch) | |
| tree | 7438ad9282bf2407f20e0ae63bfcfdf899bc9b0f | |
| parent | 97ce0fe2b7240d47d9124daa92217e478c21a3ba (diff) | |
VMCI: fix race between vmci_host_setup_notify and vmci_ctx_unset_notify
During our test, it is found that a warning can be trigger in try_grab_folio
as follow:
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1678 at mm/gup.c:147 try_grab_folio+0x106/0x130
Modules linked in:
CPU: 0 UID: 0 PID: 1678 Comm: syz.3.31 Not tainted 6.15.0-rc5 #163 PREEMPT(undef)
RIP: 0010:try_grab_folio+0x106/0x130
Call Trace:
<TASK>
follow_huge_pmd+0x240/0x8e0
follow_pmd_mask.constprop.0.isra.0+0x40b/0x5c0
follow_pud_mask.constprop.0.isra.0+0x14a/0x170
follow_page_mask+0x1c2/0x1f0
__get_user_pages+0x176/0x950
__gup_longterm_locked+0x15b/0x1060
? gup_fast+0x120/0x1f0
gup_fast_fallback+0x17e/0x230
get_user_pages_fast+0x5f/0x80
vmci_host_unlocked_ioctl+0x21c/0xf80
RIP: 0033:0x54d2cd
---[ end trace 0000000000000000 ]---
Digging into the source, context->notify_page may init by get_user_pages_fast
and can be seen in vmci_ctx_unset_notify which will try to put_page. However
get_user_pages_fast is not finished here and lead to following
try_grab_folio warning. The race condition is shown as follow:
cpu0 cpu1
vmci_host_do_set_notify
vmci_host_setup_notify
get_user_pages_fast(uva, 1, FOLL_WRITE, &context->notify_page);
lockless_pages_from_mm
gup_pgd_range
gup_huge_pmd // update &context->notify_page
vmci_host_do_set_notify
vmci_ctx_unset_notify
notify_page = context->notify_page;
if (notify_page)
put_page(notify_page); // page is freed
__gup_longterm_locked
__get_user_pages
follow_trans_huge_pmd
try_grab_folio // warn here
To slove this, use local variable page to make notify_page can be seen
after finish get_user_pages_fast.
Fixes: a1d88436d53a ("VMCI: Fix two UVA mapping bugs")
Cc: stable <stable@kernel.org>
Closes: https://lore.kernel.org/all/e91da589-ad57-3969-d979-879bbd10dddd@huawei.com/
Signed-off-by: Wupeng Ma <mawupeng1@huawei.com>
Link: https://lore.kernel.org/r/20250510033040.901582-1-mawupeng1@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/misc/vmw_vmci/vmci_host.c | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/drivers/misc/vmw_vmci/vmci_host.c b/drivers/misc/vmw_vmci/vmci_host.c index abe79f6fd2a7..b64944367ac5 100644 --- a/drivers/misc/vmw_vmci/vmci_host.c +++ b/drivers/misc/vmw_vmci/vmci_host.c @@ -227,6 +227,7 @@ static int drv_cp_harray_to_user(void __user *user_buf_uva, static int vmci_host_setup_notify(struct vmci_ctx *context, unsigned long uva) { + struct page *page; int retval; if (context->notify_page) { @@ -243,13 +244,11 @@ static int vmci_host_setup_notify(struct vmci_ctx *context, /* * Lock physical page backing a given user VA. */ - retval = get_user_pages_fast(uva, 1, FOLL_WRITE, &context->notify_page); - if (retval != 1) { - context->notify_page = NULL; + retval = get_user_pages_fast(uva, 1, FOLL_WRITE, &page); + if (retval != 1) return VMCI_ERROR_GENERIC; - } - if (context->notify_page == NULL) - return VMCI_ERROR_UNAVAILABLE; + + context->notify_page = page; /* * Map the locked page and set up notify pointer. |